|Varieties beryllium vesuvianite and cyprine|
c(001), a(100), m(110), f(120), e(l01), p(111), t(331), and s(311)
|1||c, a, m, p||Penfield, Parker shaft|
|2||a, m, r, e, p, t, s||Canfield collection, Parker shaft|
|3||a, m, p (beryllium vesuvianite)||Franklin||Figure 137|
Although vesuvianite was named in all the older lists of Franklin minerals, its authentic discovery before 1899 is doubtful, green or brown tourmaline having been commonly mistaken for it. Small red crystals of simple form were noted by Penfield (179), embedded in nasonite from the, Parker shaft, and these he afterward verified by measurement (private communication to the author).
Prismatic crystal of vesuvianite showing the forms a(100), m(110), and p(111). Franklin.
Similar but more complex crystals were seen in the same association in the Canfield collection.
A mineral from the Parker shaft, described by Chester (181) as granular vesuvianite, contains too much water properly to be assigned to that species.
In 1929 Mr. Bauer discovered the presence of beryllium in crystals of a complex silicate of unknown species shortly before discovered at Franklin. Crystallographic and optical tests established the mineral as vesuvianite, a determination with which the analysis was in agreement.
The new variety is found in slender brown prisms embedded in a coarsely granular mixture of green willemite, brown garnet, leucophoenicite, barite, minor amounts of svabite, gageite, and native copper.
The crystals show a simple combination of the unit pyramid, the prism of the first order, and the base, as shown in figure 137. They are of poor quality for measurement, as is so common with crystals of vesuvianite. Thirteen values of r for p(111) on four crystals gave an average value of 36° 52', which gives the element c = po as 0.5303; Dana uses the value c = 0.5372.
The new variety is optically uniaxial and negative, with absorption in blue light w > e , and refractive indices w = 1.712, e = 1.700. The specific gravity is 3.385 ±0.002.
The fibrous copper-bearing variety cyprine was first observed by the author in 1905 in a small dump of unknown origin at the mouth of the Parker shaft. It was in bundles of slightly radiate needles scattered through a coarse-grained feldspathic pegmatite. It is abundant in the specimens and is conspicuous, as its color is blue to blue-green. With it are manganophyllite, yellowish garnet, and native copper in threads and irregular fragments.
As the mineral was not at first recognized as cyprine but was thought to be a new species, material for analysis was separated by crushing and handpicking and careful rejection of all traces of the associated metallic, copper, as the mineral itself contains copper in combination. Analysis 1 is similar to that of cyprine from Tellemarken, Norway, but differs from it in details.
In 1922 cyprine was found in abundance in the mine at Franklin, in a crosscut about 400 feet southwest of the Parker shaft and near the 850-foot level, and in the ore body but near the hanging wall. The cyprine was rather coarsely fibrous and was intimately intermingled with brown garnet, pale-pink bustamite, white willemite, and calcite. Part of it was of vivid sky-blue color, and part of it was bluish-green. Polished surfaces of the, blue cyprine presented a striking appearance. The refractive indices of the material of the several colors are as follows:
|Blue-green cyprine, in pegmatite||1.696||1.710|
|Sky-blue cyprine, in ore||1.705||1.713|
|Green cyprine, in ore||1.712||1.719|
The abundant cyprine found later at Franklin has been analyzed by Shannon (224) and by Bauer (225). The analysis by Bauer, no. 3, was made on material nearly one-third of which consisted of willemite, as seen in thin section, and which also contained minute specks of metallic copper. Mr. Bauer has also furnished the author with two previously unpublished analyses, nos. 4 and 5, of the green and blue portions, respectively, of a single specimen of the mineral, separated by hand picking. The specific gravity of the green portion was 3.45. The difference in color of the two portions does not seem to indicate much difference in composition.
Vesuvianite is a calcium aluminosilicate of complex and variable composition, for which no simple formula has yet been generally adopted. The chemical character of the Franklin vesuvianite is shown by the following analyses:
Analysis 6, made by Bauer (272) on a picked sample of the crystals found in 1929, shows the presence of more than 9 percent of beryllium oxide. The probability that beryllium would be found at Franklin in some form was foretold by the observation, by the German spectroscopist Eberhard (200) in 1912, of beryllium lines in the arc spectrum of Franklin willemite. As yet beryllium has not been detected in wet analyses of cyprine, though it may have been present and have been determined with the aluminum. Mr. Nitchie, formerly of the New Jersey Zinc Company's laboratory at Palmerton, Pa., found that cyprine shows spectroscopically strong lines of beryllium, although relatively less strong than in spectrograms of brown beryllium vesuvianite.
It now appears certain that the beryllium is not genetically associated with the primary willemite ore but is a post-ore element introduced into the deposit from intrusive pegmatite.
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